What you've been listening to is going to be pasted all over your profile and distributed through various next-gen FB apps. Of course, that's what you've been listening to on Spotify. And what you've been watching on NetFlix.
Your "friends" (we all know that term is used pretty loosely at FB) will have a chance to hear the music or see some of the material, and if they're Spotify subscribers, to download the music.
It actually makes a lot of sense in terms of pushing music via word of mouth, and is sort of like having access to somebody's mixed tapes.
This is what Ping should have been, and perhaps would have been had negotiations not blown up with Facebook. Now Apple will probably be sorry that they didn't make the deal.
There are a lot of music and video partners involved in this project, and Apple is the obvious one that is notably absent, especially given that they are not only the largest music vendor online, but the largest music vendor full stop.